Feasibility study to assess the pollutant load of sediments as a result of the July flood 2021 in the transition from the low mountain range to the lowland area
Final Report Abstract
Many towns in NRW and RLP were affected by extreme flooding between July 13 and 16. The Precipitation sums within 48 hours exceeded mean sums for the entire month of July. During the floods, water levels peaked. Since flood events are rare, the distribution of pollutants from the floods is not known in advance. The earliest reports of floods on the Rur River date back to the early Middle Ages, more recently documented extreme floods occurred in 1890, in December and January 1902/1903 and in June 1905. On the Inde River, floods regularly occur in the winter months with high precipitation, popularly known as "Advent floods". In 18 of 25 documented flood events since 1890, the flooding took place in the winter months. Most of the floods occurred between gauge heights of 2.0 m and 2.5 m on the Inde River, i.e. discharge values of just under 60 m³/s to 90 m²/s. However, a flood event with a statistically reoccurrence period of 1 in 100 years remained unachieved until 2021. The flood in July 2021 showed the influence of topography on the hydraulics of the flood wave. Beginning in the low mountain range, water masses quickly accumulated during the heavy rain event into a steep flood wave with high flow velocities, high erosion potential, and transport capacity that transported large debris, rocks, trees, and even cars. Debris, driftwood and objects carried in the flow, especially trees, caused clogging at bridge culverts, initiating or enhancing erosion processes. Resulting backward erosion occurred mainly behind bridges or at overtopped structures. An impressive example of backward erosion could be observed during the July 2021 flood at the Inden open pit lignite mine. Numerical modelling in the urban area of Eschweiler showed that almost the entire flooded area was covered by a thin sediment layer <10 cm. In areas of low currents, thicknesses of > 50 cm were reached. %. Depending on the concentration, trace metals can pose a health risk to the public. Concentrations of Zn, Pb, Cd, Cu and As in flood sediments exceed international limits. Especially for Pb and Zn, enrichments were found in sediment samples that clearly exceeded the so-called "Probable Effect Concentration" above which damage to benthic organisms is deemed probable. Cu, As and Cd exceeded the PEC by 150-500 A simple intake assessment shows that the tolerable daily intake level for Pb is exceeded. High levels of Zn and Pb were found immediately downstream of industrial areas. Numerous potential sources of heavy metals are located along the Vichtbach River in the form of industrial operations and contaminant dumps. Relationships between pollutant sources and heavy metal accumulations can only be assumed and not proven.
Publications
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Das Hochwasser 2021 in Nordrhein-Westfalen und Rheinland-Pfalz : Beobachtungen und Erfahrungen. In: Institut für Siedlungswasserwirtschaft der RWTH Aachen University. Wasserwirtschaft im Klimawandel. digitale 55. Essener Tagung für Wasserwirtschaft. Aachen, Gesellschaft zur Förderung des Instituts für Siedlungswasserwirtschaft an der RWTH Aachen e.V.
Schüttrumpf, H.; Büll, C.; Klopries, E.-M.; Lehmkuhl, F. & Wolf, S. S.
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Das Juli-Hochwasser 2021 in NRW - Ein erster Erfahrungsbericht. Wasser und Abfall, 23(7-8), 14-17.
Schüttrumpf, Holger
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Fluviale Morphodynamik und Sedimentkontamination bei Extremereignissen: Das Juli- Hochwasser 2021 im Inde-Einzugsgebiet (Nordrhein-Westfalen). Korrespondenz Wasserwirtschaft, (15), 422–427.
Lehmkuhl, F.; Weber, A.; Esser, V.; Schulte, P.; Wolf, S. & Schüttrumpf, H.
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Assessment of the 2021 summer flood in Central Europe. Environmental Sciences Europe, 34(1).
Lehmkuhl, Frank; Schüttrumpf, Holger; Schwarzbauer, Jan; Brüll, Catrina; Dietze, Michael; Letmathe, Peter; Völker, Carolin & Hollert, Henner
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Das Hochwasserereignis 2021. In: im Auftrag des Rektors. RWTH Themen. Hochwasser – Beiträge zu Risiken, Folgen und Vorsorge. Aachen, 28–31.
Schüttrumpf, H.
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European toxic flood – methods for contaminated sediment assessment. Session A2 | Effects of extreme events on water quality. 12. Water Research Horizon Conference 2022 - Aquatic Ecosystems between Conservation & Exploitation, Essen , Germany , 2022-09-27 - 2022-09-28.
Büll, C.; Wolf, S. S.; Weber-Bernard, A. C.; Schulte, P.; Lehmkuhl, F.; Hollert & H. Schüttrumpf, H.
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Geomorphologen und Wasserbauingenieure betrachten die Auswirkungen des Juli-Hochwassers. In: im Auftrag des Rektors. RWTH Themen. Hochwasser – Beiträge zu Risiken, Folgen und Vorsorge. Aachen, 12–17.
Brüll, C.; Esser V.; Lehmkuhl, F.; Schulte & P. Wolf, S.
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Schadstoffverlagerungen bei Hochwasserereignissen. In: im Auftrag des Rektors. RWTH Themen. Hochwasser – Beiträge zu Risiken, Folgen und Vorsorge. Aachen.
Esser, V.; Wolf, S.; Schwanen, C.; Schulte, P.; Brüll, C.; Lehmkuhl & F. Schüttrumpf, H.
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Sediment pollution and morphodynamics of an extreme event: Examples from the July 2021 flood event from the Inde River catchment in North Rhine-Westphalia . Copernicus GmbH.
Lehmkuhl, Frank; Esser, Verena; Schulte, Philipp; Weber, Alexandra; Wolf, Stefanie & Schüttrumpf, Holger
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The risk may not be limited to the flooding – Polluted high flood sediments pose a health threat to the unaware public. Research Square Platform LLC.
Weber, Alexandra; Wolf, Stefanie; Becker, Nadine; Märker-Neuhaus, Leonie; Bellanova, Piero; Brüll, Catrina; Hollert, Henner; Klopries, Elena-Maria; Schüttrumpf, Holger & Lehmkuhl, Frank
